The present invention relates to a purified and highly crystallized synthetic diamond thin film, a method for producing it, an apparatus for producing it, and a device to which the thin film is applied.
It is said that the substrate temperature necessary for growth of a synthetic diamond (hereinafter merely referred to as "diamond") thin film is 750.degree.-900.degree. C. ["Kagaku to Kogyo""(Chemistry and Industry)", Vol. 39, No. 6, pp. 429-431]. According to the data which have hitherto been disclosed in patents and literatures, most of the diamond thin films were grown within the above range of substrate temperature. [Japanese Patent Kokai (Laid-Open) Nos. Sho 62-265198 and Hei 1-230496]. Therefore, high-melting point materials such as silicon and quartz have been generally used as substrates used for growth of diamond thin films. Furthermore, there has been a problem that the synthesized thin films contain impurities comprising amorphous phases in addition to the diamond and so are low in crystallinity.
As mentioned above, the diamond thin film obtained by growing diamond on a substrate heated to high temperatures is inferior in qualities such as purity and crystallinity and there are problems in its use as materials for semiconductor devices, light emitting devices or optical devices for opto-electronics.